Techniques of producing organic electronic devices using organic materials enable the integration of displays, circuits, cells, sensors, etc. on flexible plastic substrates at low temperatures, approximately equivalent to room temperature, by the use of coating and printing processes. These techniques are advantageous because electronic devices may be inexpensively formed on large flexible substrates.
However, organic electronic devices are vulnerable to the permeation of moisture or oxygen. In particular, many kinds of polymer substrates, due to their high moisture and oxygen permeability, are difficult for use in OLED flexible displays. Thus, in order to manufacture organic electronic devices having a long lifespan, encapsulation techniques for blocking the permeation of moisture and oxygen are required. Although the upper surface of organic electronic devices was initially encapsulated with glass or a metal lid, moisture could still permeate through the sealant between the substrate and the encapsulation layer. Furthermore, because the encapsulation layer is inflexible, it is difficult to apply to flexible devices. To overcome the problems of the glass or metal lid, research into encapsulation techniques using inorganic thin films, organic thin films or organic/inorganic multi-layer thin films having a combination thereof is ongoing.
Regarding conventional techniques for organic photoelectric coatings, the coating method of a multi-layer encapsulation structure including an inorganic layer and a polymer layer using vacuum equipment is exemplified. This method allows an organic device to be protected from moisture and oxygen by using a multi-layer encapsulation structure including an inorganic layer and a polymer layer joined by means of heat and electromagnetic radiation. In addition, a method for manufacturing a flexible display apparatus involves a technique applying an organic device onto a plastic substrate. This technique involves the fabrication of a thin film transistor and an organic light emitting device by forming a barrier layer on the surface of the plastic substrate.
The conventional encapsulation technique enables the device to be insulated from moisture by incorporating an inorganic thin film layer composed mainly of SiO2, SiNx, In2O3, etc. using chemical vapor deposition. However, this technique is problematic because pinholes may be formed upon deposition of the inorganic thin film, and defects may be caused due to physical damage when applied to flexible devices, undesirably resulting in permeation of moisture and oxygen. Briefly, functionality of the encapsulation film is easily lost. In order to reduce defects in the encapsulation layer due to such bending, alternate means of stacking inorganic thin films and polymer thin films are currently being studied.
Meanwhile, in order to form a thin film while suppressing the formation of pinholes in the thin film, research into fabrication of an inorganic thin film comprised of Al2O3, SiO2, TiO2, etc. using atomic layer deposition based on a self-limiting reaction has been carried out. However, this method is difficult to apply to production processes because of a low deposition rate of about 0.1 nm per cycle.